The genetics of adaptive racial differences between races of the mutually mimetic butterflies Heliconius melpomene and Heliconius erato is being investigated with special reference to: a. the occurrence and causes of 'beanbag' evolution. b. the role of linkage in this process. c. the influence of the naturally selected solour pattern genes in evolution of loci controlling allozymes. We are investigating the genetic control of recombination in silkworms.